I think there's something really interesting about the slasher necromorph design
The presence of a second set of arms isn't consistent across ALL slashers, but it is fairly common. What's really interesting is that sometimes the extra limbs are the original arms, made vestigial by the new bladed limbs. Other times, the original arms sprout the blades and a second set of arms emerges from the torso. This suggests that this is an intentional choice by the marker/guiding intelligence that controls the necromorphs and not just happenstance.
But something it does evoke is the 6 limbed Tau Volantis aliens introduced in Dead Space 3.
The hunched posture, the set of long fore-limbs and a shorter middle pair emerging from the torso, the resemblance is definitely there. It's worth remembering that these aren't necromorphs, this is the natural state of the Tau Volantis aliens.
So, is it possible that the slasher is the marker's imitation of this alien form? Human bodies twisted into the silhouette deemed more useful?
Could this be true of other, more alien necromorph body plans?
Could the leaper and infector be the marker's memories of other species that fell prey to its influence?